Cooper J A, van der Zee H, Line B R, Malik A B
Department of Radiology, Albany Medical College of Union University, Albany, New York 12208.
J Appl Physiol (1985). 1987 Oct;63(4):1586-90. doi: 10.1152/jappl.1987.63.4.1586.
We investigated the dose-response effect of positive end-expiratory pressure (PEEP) and increased lung volume on the pulmonary clearance rate of aerosolized technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA). Clearance of lung radioactivity was expressed as percent decrease per minute. Base-line clearance was measured while anesthetized sheep (n = 20) were ventilated with 0 cmH2O end-expiratory pressure. Clearance was remeasured during ventilation at 2.5, 5, 10, 15, or 20 cmH2O PEEP. Further studies showed stepwise increases in functional residual capacity (FRC) (P less than 0.05) measured at 0, 2.5, 5, 10, 15, and 20 cmH2O PEEP. At 2.5 cmH2O PEEP, the clearance rate was not different from that at base line (P less than 0.05), although FRC was increased from base line. Clearance rate increased progressively with increasing PEEP at 5, 10, and 15 cmH2O (P less than 0.05). Between 15 and 20 cmH2O PEEP, clearance rate was again unchanged, despite an increase in FRC. The pulmonary clearance of aerosolized 99mTc-DTPA shows a sigmoidal response to increasing FRC and PEEP, having both threshold and maximal effects. This relationship is most consistent with the hypothesis that alveolar epithelial permeability is increased by lung inflation.
我们研究了呼气末正压（PEEP）和肺容积增加对雾化锝-99m标记的二乙三胺五乙酸（99mTc-DTPA）肺清除率的剂量反应效应。肺放射性清除率以每分钟减少的百分比表示。在麻醉的绵羊（n = 20）以0 cmH2O呼气末正压通气时测量基线清除率。在2.5、5、10、15或20 cmH2O PEEP通气期间再次测量清除率。进一步的研究表明，在0、2.5、5、10、15和20 cmH2O PEEP下测量的功能残气量（FRC）逐步增加（P < 0.05）。在2.5 cmH2O PEEP时，清除率与基线时无差异（P < 0.05），尽管FRC较基线增加。在5、10和15 cmH2O时，清除率随PEEP增加而逐渐增加（P < 0.05）。在15至20 cmH2O PEEP之间，尽管FRC增加，但清除率再次无变化。雾化99mTc-DTPA的肺清除率对FRC和PEEP增加呈S形反应，具有阈值效应和最大效应。这种关系与肺膨胀增加肺泡上皮通透性的假设最为一致。
